Dark Bands in the Submarine Nankai Accretionary Prism – Comparisons with Miocene–Pliocene Onshore Examples from Boso Peninsula - Accretionary Prisms and Convergent Margin Tectonics in the Northwest Pacific Basin - page 239

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5 cm

N

DB-2

DB-2

MS-2

MS-1

DB-1

DB-1

DB-1

SS DB-1

SS

DB-1

a

MS-2

F

R Y

MS-1

1 mm

e

MS-2

DB-2

pattern 2
pattern 3

MS-1

pattern 1

DB-1

pattern 1

1 mm

SS

b c

0.1 mm

f

pattern 2

Y

pattern 3

pattern 1

E

R

d

g 0.1 mm

1 mm

Fig. 7 ( a ) Cut-section photo and sketch of the 6K#893 R-3 sample. In the sketch, the arrow
shows slip direction and the dotted lines are bedding planes. ( b ) Photomicrograph around DB-1
and DB-2 (open nicols). DB-1 is at the boundary between SS and MS-1, and is divided into three
patterns (see text). DB-2 is between MS-1 and MS-2. MS-1 and MS-2 are the same lithofacies,
but the attitudes of the bedding planes are different. ( c ) Photomicrograph around DB-2 (crossed
nicols). MS-1 and MS-2 show drag at the DB-2 boundaries. Additionally, Riedel shear is observed
in DB-2. ( d ) Photomicrograph around DB-1 (crossed nicols) in which shear planes are developed.
( e , f ) Photomicrographs of the boundary between DB-1 and SS: particles are arrayed in two direc-
tions, indicating right-lateral displacement, as shown in ( g )

samples (Fig. 8e ). The boundaries between DB-1 and SS or MS-1 are sharp at
mesoscopic scale, but they are obscured at the microscopic scale of the SEM
(Fig. 8a, b ). Scaly clay flakes were observed in places on the boundary between SS
and DBN-1 and in DB-1.